In a power generation plant, operators or maintenance engineers need to be able to change a control parameter or logic of a control program during operation of a control arithmetic device that executes the control program in the power generation plant. The control parameter or logic is changed by a terminal in a central control room (an operator station or an engineering station). Therefore, a method of changing a configuration file or a control program online has been developed (refer to Patent Documents 1 and 2).
At this time, in order to prevent the plant from becoming unstable by setting the parameter of the control program to an incorrect value or changing to an incomplete logic by the operators or the maintenance engineers, such a change is preferably checked before changing. As a method of preventing such misoperations, a method of checking a version of the program (refer to Patent Document 3) and a method of checking whether a person has the authority to edit the program or not (refer to Patent Document 3) have been disclosed.
Further, an international functional safety standard (IEC (International Electrotechnical Commission) 61508 and JIS (Japanese Industrial Standards) C 0508) recommends that means for preventing misoperation in order that the operators do not change to the incorrect control program be adopted.